Indy cars will travel at a top speed of about 235 mph during their time trials before the Indy 500. However, their final speeds posted to determine starting positions are usually 10-15 mph less. Why?

Answer(a)   the matererials that are in contact, the two materials and the nature of their surfaces/// (b)/// the force pushing the two surfaces together, pushing the surfaces together causes the more of the asperities to come together and increases the surface area in contact with each other

Imma say go with a (: